Re: IC-7600; Mode:RTTY and AFSK?


Rich Seifert
 


On Nov 16, 2015, at 10:29 AM, uwe.dl4ac@... [N1MMLoggerplus] <N1MMLoggerplus@...> wrote:

 

Hello,

I wonder, if it is possible to receive RTTY in IC-7600-Mode "RTTY" and transmit AFSK generated by N1MM+?

At the moment I am using LSB-D1 to receive and transmit AFSK via USB. Downside of this: I can't use the Twin-Passband-Filter of my IC-7600.

73 de Uwe, DL4AC



Short answer is no. If you choose AFSK as your generation method, you must use a Digital SSB mode, which cannot use the TPF. If you choose FSK for transmit, you put the radio in RTTY mode and the TPF is available.

That said, I believe MMTTY has a TPF available in software. Does it really matter whether the hardware or the software does the filtering? I’m not even sure which one is a “better” filter. That said, I use FSK on my 7600 and enable the TPF. (I use a Microkeyer-II to do the FSK generation, as this is not possible through the USB connection.)

Now with all THAT said, believe it or not, what the radio does INSIDE in RTTY/FSK mode is to use the FSK signal to generate a pure tone in the DSP, which the radio injects into the SSB chain. That is, it’s AFSK in the radio either way. The advantage of treating it like FSK externally is that there is no need to make precise audio adjustments (ALC, etc.) and no need to keep a “clean” audio path from the computer to the radio.

Rich KE1B

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